1. Field of the Invention
The present invention relates to a method for interoperating MMT media and DASH media.
2. Discussion of the Related Art
New standards, such as MPEG-4, H.264/AVC, and Scalable Video Coding (SVC), for a video compression standard (or an audio compression standard) since MPEG-2 standardization have been continuously developed for the past ten years. Furthermore, each of the new standards has widened the utilization area of the MPEG standard while forming a new market, but delivery technology, such as a MPEG-2 Transport System (TS), has been widely used in digital broadcasting and mobile broadcasting (T-DMB and DVB-H) in the market during almost 20 years. Furthermore, the MPEG-2 TS is also being widely used in multimedia transmission over the Internet, that is, IPTV service, which was not taken into consideration when a standard for the MPEG-2 TS was established.
However, a multimedia transmission environment when the MPEG-2 TS was developed and a current multimedia transmission environment are experiencing a significant change. For example, the MPEG-2 TS standard was developed to transmit multimedia data over an ATM network when it was established, but today is rarely used for such an object. Furthermore, the MPEG-2 TS standard involves elements which are inefficient for recent multimedia transmission over the Internet because requirements, such as multimedia transmission using the Internet, were not taken inconsideration when the MPEG-2 TS standard was established. Accordingly, in MPEG, the establishment of a MPEG Multimedia Transport Layer (MMT), that is, a new multimedia transmission standard in which multimedia service in the Internet suitable for a changing multimedia environment is taken into consideration, has been recognized as a very important task.
As described above, the reason why MMT standardization is important lies in an urgent need for an international standard for multimedia transmission which has been optimized for recent multimedia transmission environments in various heterogeneous networks because the MPEG 2-TS standard established 20 years again has not been optimized for recent IPTV broadcasting service and Internet environments. For this reason, in MPEG, MMT standardization is in progress as a new delivery technology standard.
Meanwhile, the recent development of mobile communication technology has rapidly accelerated the popularization of mobile communication terminals and thus has changed our life so that most of common people always carry mobile communication terminals, such as mobile phones, PDAs, and smart phones. The mobile communication terminal has an effect that enables a user to access a communication network more easily and also enables the system resources of a conventional communication system to be efficiently distributed. From such technologies, there is provided streaming service in which multimedia content, such as audio content and video content, can be received and played back in real time over a wireless content communication network while being in motion with a mobile communication terminal carried. Streaming service applied to wired IPTV provides multimedia content through a Real-time Transport Protocol (RTP) or in a form in which the RTP and MPEG-2 are combined.
In the case of streaming service using a wireless method, however, if streaming service is provided through the RTP or in the form in which the RTP and MPEG-2 are combined, a problem arises. First, if multimedia content is divided into a plurality of packets and transmitted, there is a problem in that a plurality of ports according to the plurality of packets must be opened because the RTP does not support multiplexing. In particular, streaming service cannot be normally provided using the RTP in an area in which a firewall is installed.
Second, the RTP operates on the User Datagram Protocol (UDP). On the wireless Internet, the UDP divides multimedia content into a plurality of packets, sends the plurality of packets to a receiver, but does not check whether the transmitted packets have arrived at the receiver in the correct order. For this reason, a loss of packets may occur. Furthermore, if a loss of packets is generated, content may be lost because the lost content packets are not retransmitted to the receiver.
Accordingly, a method of providing streaming service using a Hyper Text Protocol (HTTP) that operates on the TCP is chiefly used in mobile communication terminals, such as smart phones. This is commonly called ‘HTTP streaming’.
In general, the HTTP is a protocol used to send text, such as hypertext, and images. Thus, if multimedia content streaming service is provided using the HTTP in mobile communication terminals, such as smart phones, there is a problem in that streaming service cannot be provided in real time because the amount of multimedia content is great.
In order to provide MPEG media streaming service in mobile communication terminals, such as smart phones, Dynamic Adaptive Streaming over HTTP (DASH) standardization has almost been completed.
DASH standardization is for providing MPEG media streaming service in mobile communication terminals, such as smart phones. MMT standardization is for providing improved media (e.g., media having resolution of UHD level or higher) transport service under a dynamic network environment, such as hybrid delivery.
Some of MMT use cases may need to be supported by the DASH standard in order to transport MPEG media.